Application of mud-laden fluids to oil or gas wells



Patented Mar. 9, 1926.

UNITED STATES .PATENT OFFICE.

BENJAMIN K. SIBOUD, LOS ANGELES, CALIFORNIA, ABSIGNOB TO NATIONAL PIG- KENTS & CHEMICAL COMPANY, OF ST. LOUIS, MISSOURI, A CORPORATION 01 MISSOURI.

APPLICATION OF MUD-LADEN FLUIDS TO, OIL 03 GAS Ho Drawing.

To all whom it may concern:

Be it known that I, BENJAMIN K. Srnoun, a citizen of the United States, and residing at Los Angeles, county of Los Angeles, State 5 of California, have invented the new and useful Improvement in Application of Mud- Laden Fluids to Oil or Gas Wells, of which the following is a specification.

This invention relates to mud-laden fluids,

and more particularly to their application to oil or gas wells. This ap lication is a continuation in part of my app ication Serial Number 630,399. filed Apr1l6, 1923, as to subject matter common therewith.

1 In the drilling and control of oil and gas wells mud-laden fluids are used. In rotary drilling the fluid is introduced through the drill stem to the bit and there issues to rise in the bore hole. The fluid performs not 2 only the function of a lubricant in maintaining the bit itself as well as the stem lubricated, but it also serves to carry oif the cuttings and so prevents the bit and stem from sticking or freezing in the bore-hole; the

agitation causes the cuttin s to become and remain suspended in the flhid so as to rise therewith in the bore-hole. The mud-laden fluid is introduced into the well by a slush pump while the fluid (carrying the cuttings) 80 issuing from the bore hole is discharged into a settling ditch where the cuttings settle out while the fluid is again passed to the well to complete another circult.

The mud-laden fluid also performs other useful functions even in rotary drilling operations, namely, that of mudding off and holding down heavy pressures. The passage of the fluid in contact with the unlined walls of the bore-hole and under the hydrostatic pressure of the fluid column, causes the fluid to penetrate the walls and thereby form in fact a distinct mud wall which seals or mu'ds 01f the surrounding region. Moreover the weight or head of the mud column serves to hold down heavy pressures so'that control of the well may be retained even when the pressures become high.

Mud-laden fluids are also employed to control wells generally. For this purpose-the fluid is introduced into the well in any suitable manner, as for instance with a device Application filed December 17, 1924. Serial No. 758,624.

known as a lubricator, so that the bore;hole

(gr even the casing) will become filled with t e fluid so as to over-balance the gas pressures. In this way the well may be maintained under control, either temporarily or permanently, or even killed.

The ordinary mud-laden fluid obtained at or from a well does not have the required characteristics to render it satisfactory. One of the important, if not the most important one, is that the specific gravity of the mud laden fluid be not only sufliciently high to overcome the gas pressures, but this specific gravity must be maintained. Muds mixed from a clay or a she-1y clay may be of such consistency that they can hardly be pumped and yet their specific gravity may not run over 1.3, i. e., eleven pounds to the gallon.

Such a thick mud will, however, become gas' cut, i. e., the gas aerating or working on the mud lightens the mud column to sue] an extent as to become overbalanced by the gas pressure so that the mud column willbe expelled from the well; accordingly the well is liable to pass beyond control resulting in great damage to property and loss of life or limb, and even causing craters and preventing proper finishing of the well.

When the mud-laden fluid is too thick the cuttings will moreover not drop or settle out in the settlingditch, or the time fol settling may be so long as to render itt reuse impractical. Mud made from a shale or shaly clay is moreover not sufliciently -slimy as to act properly, either as a lubricating agent for the bit or stem, or as a lastering agent for penetrating or buil ing up the walls of the bore-hole. In order to act properly in either capacity the mud-laden fluid should have slimlng properties and not abrasive properties. The action of mud ding is penetration followed by wall building upon the mud itself. The plastered wall should withstand the erosional action of the slush pumps even when clear water is pumped past it for a considerable time as is often necessary. This resistance to erosion is extremely important and it is evident that a sandy fluid would act in an opposite manner from a slimy fluid, i. e., a sandy fluid would hasten the process of erosion whether in the wall itself or whether a partof the moving columns of fluid being circulated.

One of the objects of this invention, therefore, is to provide a mud-laden fluid for oil or gas "wells, which has the properties and characteristics desired and necessary in order to adapt it for its intended uses.

Another object is to provide a process or method for producing such a mud-laden fluid.

Another object is to provide a process or method of applying such a mud-laden fluid to the boring or control of 011 or gas wells.

Further objects will appear from the detail description in which will be described a number of embodiments of this invention; it will, however, be understood that this invention is susceptible of various other embodiments.

In accordance with this invention the mud-laden fluid is characterized by the fact that it has a specific gravity considerably in excess of that of water. because the gas pressures encountered in oil and gas wells are usually equal to or greater than hydrostatic, i. e., equal or greater than the pressures of a like column of water in the wel For safetys sake the pressure exerted by the mud-laden fluid column should be considerably greater than that of a water column of the same height. In accordance with this invention the specific gravity of my mud-laden fluid is substantially in excess of that of clay laden fluids of the same and required viscosity. I have found that a mud-laden fluid having a specific gravityin excess of two meets the requirements.

The mud-laden fluid embodying this invention is, however, sufficiently thin, when of the required specific gravity, as to not only enable it to be readily pumped and as to not only readily drop or settle the outtings, while maintiining them in suspension until out of the well; but the character of the mud base and of the mud-laden fluid formed therefrom is such as to not become gascut and not cause the column to decrease in specific gravity enough so as to be expelled. The base and fluid is, however, slimy as distinguished from abrasive; accordingly not only does it perform the function of a lubricant for the bit and drill stem, but it is sufl'iciently thin to properly enetrate the wall of the bore-hole while building up a dense and non-eroding wall after such penetration, The fluid is, however, non-setting, i. e., even when not agitated, the fluid will not set to form a solid mass. Moreover the base will remain in suspension, even without agitation; it is in fact a true suspensoid. The base, as well as.

This is important the fluid formed thereby is also inert chemically, in that it does not attack the wall of the bore-hole or the casing and drilling equipment.

A base which I have found especially suitable for forming a mud-laden fluid meeting the requirements and as possessing the desired characteristics and properties, is barytes barium sulphate. It has a comparatively high specific gravity and forms a suspcnsoid which even of a specific gravity of 2.55 (21 pounds per allon) is thin enough to be readily pumpe moreover even at that high specific gravity the cuttings will readily drop or settle out. Its sliming properties adapt it not only as a lubricant but also as a wall builder; the fact that it is a pigment base shows its property as a covermg medium. It Wlll remain in suspension indefinitely, especially since it can be finely ground, 800 mesh being easily obtained. It will remain in a fluid condition and will not set as is the case with other high specific gravity substances. It does not gascut since it can be sufliciently thin while maintaining the required specific gravity. Barytes, even in its raw state is very pure, the barium sulphate content running as high as 98%; accordingly even in its crude state it is chemically inert; moreover its purity enables its specific gravity to be maintained while its sliming and other properties are maintained.

While a suitable barytes mud of even 2.5 specific gravity can be obtained, I have found that a specific gravity of two or over is sufficient. Accordingly in,order to obtain a sufficient thick mud-laden fluid in order to hold the cuttings in susension, the barytes mud can be'cut down with ordinary mud as obtainable at the well,'so as to obtain the desired mud-laden fluid of the desired specific gravity (2 or over) and of the desired viscosity. Since. barytes is white it will serve to readily indicate the presence of petroleum.

While I have foundbarytes especially suitable, other pigment bases may be used; one which I have found suitable is an iron oxide, such as ferric oxide (Fe O or red pigment; this is commonly used in paints and is substantially inert chemically; it can be used in finely divided form and forms a suspensoid, either alone or in connection with ordinary mud as found at the wells. -While, however, iron oxide is chemically inert, it is a good conductor of electric currents, while barytes is not: corrosion of casings due to electrolytic action may, therefore, take place with iron oxide, while such action will not take place when barytes is used. The sealing and penetrative qualities of iron oxide are, however, high and a mudladen fluid of a specific gravity of two may be readily obtained when using a base containing only 85% iron oxide; such a fluid will be sufficiently thin to be readily handled and it will not become gas-cut. The slimy lubricating, wall building and other properties of iron oxide mud are also desirable.

Another suitable substance or compound which may be used in an oxide of lead, such as plumbic oxide (PbO) or litharge; this compound is also commonly used in paints, is substantially inert chemically, and can be used in finely divided form and forms a suspensoid either alone or in connection with ordinary mud as found at the wells.

It will, therefore, be seen that the invention accomplishes its objects. A mud-laden fluid is obtained which will meet the conditions encoimtcred in the drilling and control of oil and gas wells. The fluid may be used as usual in drilling, control and even in the killing of wells, without being subjectto the disadvantageous features of ordinary mud. The mud may be used over and over again and may be used to increase the specific gravity and improve the properties of mud available at the wells.

It is to be understoodthat while a theory.

of operation has been advanccd, it is not the only or necessary one but-has only been advanced to facilitate the disclosure. It is understood, however, that this invention is not limited to any theory of operation or action. It is further obvious that various changes may be made in details without departing from the spirit of this invention; it is, therefore, to be understood that this invention is not to be limited to the specific details described.

Having thus described the invention, what is claimed is:

1. A mud-laden fluid for oil or gas wells characterized by' the fact that it is slimy and has a specific gravity which is substantially in excess of that of clay-laden fluids or" the same viscosity.

2. A mud-laden fluid for oil or gas wells characterized by the fact that it is nonsetting and has a specific gravity in excess oftwo.

3. A mud-laden fluid for oil or gas wells characterized by the fact that it is slimy and non-setting and has a specific gravity which is substantially in excess of that of clayladen fluids ot the same viscosity.

4. A mud-laden fluid for oil or gas wells characterized by the fact that it is chemically inert and has a specific gravity which is substantially in excess of that of clayladen fluids of the same viscosity.

5. A mud-laden fluid for oil or gas wells comprising a pigment base suspensoid.

6. A mud-laden fluid for oil or gas wells consisting of a pigment base suspensoid and having a specific gravity which is substantially in excess of that of clay-laden fluids of the same viscosity.

7. A mud-laden fluid for oil or gas wells comprising bar tes in suspension.

8. A mud-la en fluid for oil or gas wells comprising barytes in suspension and having a specific gravity which is substantially in excess of that of clay-laden fluids of the same viscosity.

9. A mud-laden fluid for oil or gas wells comprising a slimy substance, whose specific gravity is sushstantially greater than that of clay, held in suspension in a lighter suspensoid.

10. mud-laden fluid for oil or gas wells comprising barytes suspended in an earthy suspensoid.

11. In the art of boring or controlling oil or gas wells, the process comprising introducing into the well a non-setting mudladen fluid of a specific gravity which is substantially greater than that of clay-laden fluids of the same viscosity.

12. In the art of boring or controlling oil or gas wells, the process comprising introguciing into the well a barytes-mud-laden 13. In the art of boring or controlling oil or gas wells, the process comprising introducing into the well a barytcs-mud-laden fluid of a specific gravity which is substantially in excess of that of clay-laden fluids of the same viscosity.

14. In the art of boring or controlling oil or gas wells, the process comprising introducing into the well a non-setting mudladen fluid of a specific gravity which is substantially greater than that of clay-laden fluids of the same viscosity and sufiiciently thin as not to become aerated.

15. In the art of boring or controlling oil or gas wells, the process comprising introducing into the well a mud-laden fluid and controlling the density of the fluid by the addition of a slimy su'spendablc ingredient whose specific gravity is substantially greater than that of clay. 7

16. In the art of boring or controlling oil or gas wells, the process comprising introducing into the well a mud-laden fluid and controlling the density of the fluid by the addition of barytes.

17. A mud-laden fluid for oil wells characterized by the fact that it is sufliciently thick to hold the cuttings in suspension but sufficiently thin as not to become aerated and that its specific gravity is substantially in excess of that of clay-laden fluids of the same viscosity.

18. A mud-laden fluid for oil wells characterized by the fact that it is sufiiciently thick to hold the cuttings in suspension but suflicient 1y thin as not to become aerated and that its specific gravityis sufliciently high to overbalance a gas pressure substantially in excess of hydrostatic pressure.

19. In the art of boring or controlling oil or gas wells, the process comprising introducing into the well a mud-laden fluid, and maintaining the fluid sufficiently thin as not to become aerated and of a specific gravity sufficiently greater than that of clay-laden fluids so as to overhalance the gas pressure encountered.

20. In the art of boring or controlling oil or as wells, the process comprising introducing into the well a mud-laden fluid, and maintaining the fluid sufficiently thin as notto become aerated, sufficiently thick to hold the cuttings in suspension and of a specific gravity sufficient to over-balance a gas pressure substantially in excess of hydrostatic pressure. I

21. In the art of boring or controlling oil or gas wells, the process comprising introducing into the well a mud-laden fluid, and maintaining the fluid sufficiently thin as not to become aerated, sufficiently thick to hold the cuttings in suspension, and of a specific gravity sufficient as to overhalance the gas pressure encountered.

In testimony whereof I affix my signature this 18th day of November, 1924.

BENJAMIN K. STROUD.

Certificate of Correction.

It is hereby certified that in Letters Patent No. 1,57 5,945, granted March 9, 1926', upon the application of Benjamin K. Stroud, of Los Angeles, California, for an Application .of Mud-Laden Fluids to improvement m appear in the printed and 48, claim 2, strike out the words in excess of two clay-laden fluids of the same mscoszty; same page, consisting of read compfisz'ng; line 76, claim 9, t the comma andinsert instead the word and; and

stantz'ally in excess of that of line 62, claim 6, for the words after the word clay str1ke on Oil or Gas Wells, errors specificatlon requiring correction as follows: Page 3, lines 47 and'insert elihickis subthat the said Letters Patent should be read with these corrections therein that the same may conform to the record [SE-AL] of the case in the Patent Ofiice. v Signed and sealed this 13th day of April, A. D. 1926.

M. J. MOORE, Acf/ing Commissioner of Patents. 

